This invention relates to horizontal directional boring machines and more specifically to a drilling head construction which utilizes a rotating cutting blade for drilling a bore hole in conjunction with a fluid cutting jet and an inclined steering surface to steer the drill string and head in a specific direction.
Guided horizontal boring machines is a new field of technology which is replacing conventional trenching machines for the placement of utility lines, such as electricity, telephone, water and gas. The conventional manner to install or replace these utility lines was with conventional trench digging equipment where a ditch is first dug in the area where the line is desired. The utility line is then installed and the ditch is covered. While the trenching machines of today are making more narrow trenches to minimize the work and settling, the advantages of eliminating trenching completely far surpass the various problems which exist with directional horizontal boring. As for example, horizontal boring permits utility lines to be run under existing streets, highways, and landscaped yards without disturbing the surface with any type of trench or the traffic on the street. Digging a trench also creates a greatly increased chance of disturbing existing utility lines and lastly the time and labor involved is substantially reduced. Guided horizontal boring machines, also referred to as trenchless construction techniques, have become very viable and cost effective. These new guided machines can bore along a straight or veering path at any desired depth and reach an end point within two feet of its desired location. Replacement and retrofit construction of underground utility services in urban and suburban areas is an immense application for this technology.
Initial efforts of horizontal boring for utility lines were not guided, but rather commenced from a pre-dug hole drilling a horizontal unguided hole to an existing second hole or trench as typified in U.S. Pat. No. 3,451,491. there has long existed horizontal large tunnel boring machines, sometimes referred to as pipe jacking machines. However, these machines and technology are limited to large tunnel boring, while the directional boring machines of the present invention are limited to relatively small pilot boring on the order of less than 5 inches which in turn can be reamed out up to 12 inches.
The steering capability of horizontal boring machines over a variable path is achieved by various types of drilling heads which in turn use both hydraulic forms of cutting as well as mechanical cutting with hardened bits or a combination of both.
Various hole forming methods are utilized depending upon the soil conditions encountered. Some of the early directional boring machines operated down-hole tools from an umbilical supplied power source through hoses and electrical wires. In the early 1960's, AT&T Bell Laboratories developed an umbilical type guided boring device, also referred to as a percussion or impact mole which was powered by pressurized fluids and electrical lines trailing the tool. The mole was steered by an articulated body and movable fins on the mole for rotating the mole into the steering position.
The alternative to an umbilical supplied tool involved a string of flexible drill rod or tubing controlled on the surface by a drill frame which applied thrust for lineal movement and rotational torque for cutting along with pressurized fluids for cutting. The directional boring machines which are currently on the market are all the "drill string" latter type with drill frames on the surface which apply thrust, and rotation for guiding the drill string and hydraulic pressure in the case of hydraulic cutting tools. Some drill frames start their bore from the surface, such as U.S. Pat. No. 4,905,773, while 4,592,432 and U.S. Pat. No. 4,694,913. In the '432 patent, the head is guided by a movable vane on the head which is controlled at the surface. The '913 patent is guided by a fixed slanted face and precise rotation of the head.
There are various hole forming methods utilized in these guided boring machines, the uses of which are dictated by the various soil conditions. The compaction type method of hole forming basically displaces to the side the material in the bore hole and utilizes either rod pushing or a percussive drill head, such as taught in the previously mentioned '913 patent to McDonald, et al. Another method of hole forming in harder soilds is to mechanically cut the hole with a rotating hardened bit, as typified in U.S. Pat. No. 3,746,106. The mechanical cutting bit can either be dry in the case of hard dry soils or soft rock or can be supplied with a fluid stream through the drill pipe and bit with the fluid functioning to liquify and to transport the cuttings away from the drill bit.
In oil field drilling technology, which is basically vertical drilling on a different scale, there has developed a deflecting bit technology in the 1930's and 40's, as typified in U.S. Pat. Nos. 2,196,940 and 2,324,102. These directional bits, also referred to as "spudding" bits, were utilized in an oil well bore when it was desirable to change direction or guide the bore in a different direction. All of these spudding type bits utilized a canted surface on the end of the drill string for deflecting the bit and the drill string laterally during thrusting or lineal movement of the bit. While both of these spudding bit designs could be rotated to cut away the bore hole, they were basically used only for non-rotative thrusting action.
Aside from mechanically cutting the bore hole, another technique, generally referred to as fluid cutting with the use of high velocity fluid jets, are utilized in certain softer soils, as typified in U.S. Pat. No. 4,674,579 to Geller, et al. These high pressure low volume jets hold the cuttings in suspension and form a slurry while the head compacts the slurry into the bore wall for supporting the hole. Some boring machines, such as the present invention, utilize a combination of mechanical cutting along with low volume high pressure fluid cutting. U.S. Pat. No. 4,953,638 to Dunn also typifies a dual cutting operation wherein a flat cutting blade is inclined whereby it acts as a turning surface when it is not rotating.
U.S. Pat. No. 4,679,637 to Cherrington, et al, also teaches a dual cutting head wherein an inclined ramp on the front of the head cuts when rotated and turns the head when rotation stops.
The various methods for steering the drill head include a slanted face, a bent head, an angled fluid jet, a movable vane and various combinations thereof. All of these steering methods create a side force on the drilling head as the head is thrusted forward in the soil. If the head is being rotated during this thrusting action, the lateral forces cancel each other out during a complete rotation of the head and the bore path is substantially straight. However, when it is desired to turn the head in a certain direction, the rotation is stopped with the angled face or angled jet pointing in the direction of the turn and then the drill string is thrusted forward thereby effecting a turn. The location of the down-hole drilling head and the angular position of the steering surface is electronically sensed on the surface from a radio transmitter located within the drilling head. The previously mentioned patent to Geller, et al illustrates typical electronics circuits for determining the angle and location of the head in its down-hole position. The Geller, et al patent is the most widely used and accepted directional boring apparatus used throughout the world with a steering head which is bent and utilizes an angled fluid jet. The steering head is moved to the desired rotational orientation of the angled jet and then advanced into the bore hole without further rotation.